Today I finally tested the FEAR Steam version and find out It works for multiplayer!
All you need is a Valid Multiplayer key, like the ones you can get in fear-combat.org
Also you need to create the key.ini manually, but that’s easy.
Instructions here: http://fear-community.org/help/help-cd-key-verification-failed/
I guess I don’t need to say how good this is, basically all steam FEAR players can play online ^_^